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v3.25.3

Business segment data - Narrative (Detail) | 9 Months Ended
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Sep. 30, 2025 Activity
Segment Reporting [Abstract] |
Number of insurance segment activities | 2

X
- Definition Number of insurance segment activities + References No definition available. + Details
Name: | brka_NumberOfInsuranceSegmentActivities
Namespace Prefix: | brka_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_SegmentReportingAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration